Latest ecpg patch broke MSVC build

This morning's ecpg patch certainly seems to have been snake-bit.
Although the Windows gcc buildfarm members seem happy, the MSVC ones
are all failing with

Linking...          Creating library Release\libecpg\libecpg.lib and object Release\libecpg\libecpg.exp
libecpg.exp: error LNK2001: unresolved external symbol DllMain@12       .\Release\libecpg\libecpg.dll : fatal error
LNK1120:1 unresolved externals
 

I see that DllMain() got added to misc.c, so it's not obvious what's
wrong here.  Some adjustment needed in the MSVC build scripts maybe?
        regards, tom lane